We humans are a hopeful bunch — so hopeful, in fact, that our views of the future are often irrationally positive. But at what point does unflagging optimism become detrimental to our progress and success? Is there any chance that our starry-eyed tendencies could actually work in our favor, or do they simply leave us unprepared for future misfortunes?

This line of inquiry is inspired by a study published last October in Nature Neuroscience, wherein researchers used neuroimaging techniques to identify which regions of the brain are responsible for maintaining what psychologists and neuroscientists call "optimism bias," or — as the researchers put it — "unrealistic optimism... in the face of reality."

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Neuroscientist Tali Sharot and her colleagues asked test participants to estimate their chances of experiencing 80 unfavorable events (falling ill, for example, or being the victim of a crime). Participants were then told the actual average likelihood of each event, and given the opportunity to revise their estimates.

Seventy-nine percent of the test subjects paid more attention when the actual risk of an event was lower than their initial guess, and rated their risk significantly lower when given the chance to revise their initial estimate. Paradoxically, those who had underestimated their odds of experiencing an unfavorable event were much less likely to adjust their estimate the second time around (if they adjusted it at all). SciAm's Andrea Anderson describes what the researchers observed in the way of brain activity:

Using functional MRI, the resear­chers found areas in the prefrontal cortex, where conscious reasoning takes place, that were active when participants received infor­mation that was better than anticipated. The greater the difference between the subjects' initial guess of their risk and the true probability, the more activity appeared in these regions, hinting that they contribute to positive error correction.

Activity in another part of the brain, the right inferior frontal gyrus, changed in response to discouraging information. There, however, activity did not correspond as closely with the magnitude of error in the participants' initial risk estimates, matching the poorer correction later. That incon­sistent neural response was ob­served most clearly or most often in individuals who scored higher on standard tests for optimism as a personality trait. [Emphasis added]

In other words, explain the researchers, "participants updated their beliefs more in response to information that was better than expected than to information that was worse." What's more, this lapse in "belief updating" was linked to specific brain activity — highly optimistic individuals actually demonstrated a "failure to code for errors that should reduce optimism."

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It's easy to imagine how an optimistic bent could work against a person. It stands to reason, for example, that an unrealistically positive person would be less likely to take precautionary measures against future risk than, say, someone with a more realistic (or even pessimistic) outlook on life. And yet, according to Anderson, previous studies have observed an optimism bias in roughly 80% of the human population, which suggests that four out of five people may be walking around with "faulty" belief-updating brain wiring. The absence of an optimism bias has been linked to anxiety and depression; and people with positive outlooks tend to have lower stress and anxiety levels than those who see the glass half empty. Based on our (admittedly limited) understanding of optimism bias and its neural mechanisms, observations such as these would suggest that there is, in fact, some evolutionary advantage to unflagging positivity.

Then again, if one wants to approach the question of optimism's advantages from an evolutionary angle, it would help to do so on a broader scale. One can't help but wonder how studies like Sharot's might benefit from a larger sample size (the study looked at just 19 participants), greater sample diversity (test subjects were between the ages of 19 and 27), or even a broader geographical reach (it's unlikely that 19 volunteers in a university study offered much in the way of global representation).

And what of temporal resolution — by which I mean: how does the optimism of a 21st century Londoner compare to that of a Great Depression-era American, or hell, that of a foraging protohuman? Is it possible that optimism bias and its neural correlates are simply symptomatic of our particular historical moment?